the Cheshire Cat smiles

Please ignore the following posts until I prepare them to be moved into higher sections.

Thank you.

the sciencechatforum dot com does not have a sandbox section. I have decided to use the lounge area as a sandbox for preparing formatted text. I use a lot of formatting in my posts, and for very long posts this editing becomes cumbersome. The editing is hard keep up with given that there is a time-line cutoff on this forum for editing posts. As this topic becomes near book-length expository, I might want to perform more 'scholarly' techniques like removing sections and elaborating more on ambiguous parts.

Re: the Cheshire Cat smiles

Debates rage like wildfires around the Interpretations of Quantum mechanics. We can bring the topic into crystal clarity by reframing the issue from the perspective of the metaphysics of the ancient Greeks. We can capture the essence of why this question bothers us so much, by consulting the idea of Plato's Cave.

Long story short. {{ We humans only ever measure particles in the world around us. But when we are not measuring a physical system, the system will go into a state known as the Schroedinger wave. In the small gaps between measurements the "particles" are no longer particles, but smeared-out probabilities, as if they are everywhere at the same time and in every state at the same time. These Schroedinger waves even defy the uniqueness of the particle's identities. In very cold physical systems, a collection of particles will not have individual identities, but act in concert as a singular 'grouping' of Schroedinger wave comprising them all. Again, whenever we go to measure the system directly, it 'snaps' back into a particle again. }}

Plato believed that we do not experience reality directly, but only perceive 'shadows on a cave wall'. The real underlying reality is the fire and the objects that cast the shadows. You may be seduced into thinking that 2000 years of science and technological development has laid this question to rest. Instead, quantum mechanics has shown us that we have made absolutely no progress on the question at all.

Consider a down-to-earth example. If you place two microscopic flat pieces of glass near each other so that you form a tiny gap between them around distance 'comparable to the wavelength' of the light -- you will get 'thin film' effects. There is a particular 'magical distance' between the glass plates where all incoming photons will reflect totally from the top plate. There is another magical distance where all the light will pass through the top plate and reflect from the bottom one, and go back out through the top. If you move the bottom plate in _either direction_ up or down, moving away from the magical distance, then some continuous percentage of the photons will transmit and reflect from the bottom. As you move away that percentage will grow until it reaches 100%. Continue separating and the percentage goes back down again.

Here's the trick : The bottom plate is obviously 'causing' the incoming photons to completely reflect from the top plate , because when I move it just an iota, some of the photons will begin to transmit. I can move it an iota in either direction. In the configuration in which 100% of the photons reflect from the top plate, how pray tell, do those photons 'know' there is a plate underneath? Those photons never went down there to interact with the bottom plate. They know it is there, but never touched it. What is going on?

Re: the Cheshire Cat smiles

Modern science gives us the answer. But the answer will bring plato right back into our faces (as I will show below)

The modern 'answer' to this question is that the photons themselves do not know there is a plate there, but this wave in space called the Schroedinger Wave does. BEcause it knows everything.

the Schroedinger wave plays teh same role with all particles known to science. The schroedinger wave is why photons will 'slow down' and 'change direction' when passing through transparent glass. This is glass that is not absorbing the photon. INdeed -- every particle interaction known to science works the same way with the Schroedinger wave.

{{Add something above}} that the presence of the bottom plate will 'disturb/effect/change/mutate' the Schroedinger wave in the local portion of space between and among/within plates. Draw analogy with a window glass pane also does this and that's what causes snell's law of refraction {{et cetera mix and match}}

So what is the Schroedinger wave?

( add variat -- clearly modern physics has resolved such a question. _

Get a bunch of Ph.d holding professors in the room. With their 3-page long CVs, and their office walls lined with university degrees and their tweed jackets with patches on the elbows and their big grey beards. Speaking in soft voices about their "distinguished colleague" Get um all in a room. Ask them this question: IS teh Schroedinger wave a REAL OBJECT in space out there? Or is just a computational device we use on the chalkboard?

Slowly but surely, if you tease them out of their shells. you will find that every tweed-jacket wearing professor in teh room has a STRONG OPIONION about this.

And more importantly none of their answers agree. There is no consensus among them.

( edit format bullet point list)

Half of the professors will tell you that the Schroedinger wave is a real object out in space somewhere, and that particles are merely "local perturbations" in the universal fields. (add mention Quantum everette Many Worlds interp_

Another 25% of them will tell you that the particles are real, and the schroedinger wave is just a computing device for founding out how they behave. (add mention copenhagen interp)

And yet some others will tell you that the Schroedinger wave represents the "measure of ignorance" a distant observer has about the state of a system (add mention Quantum Bayesianism interp)

Re: the Cheshire Cat smiles

Now that I've covered the basics, we can circle the wagons and bring Plato back in to this dialogue.

The schroedinger wave itself can take on any plausible value that a "wave" can take on in space. And generally the mecahanism of QM allows this. However, whenever we go to actually measure a physical system, we only ever find it in an "eigenstate".

Dont be put off by the mathematics --- 'eigenstate' reoughly corresponds to a 'standing wave'

So QM dictates that the schroedinger wave evolves in time continuously like a wave, but every measurement we humans ever make only show the 'particles' in an eigenstate. In the case of an electron we never ever see one of them 'on its way' to another eigenstate, after say, absorbing a photon.

An electron will be found to be in an s-orbital or an a p-orbital, but never anywhere else. NEver is it foudn to be "on its way" to a p-orbital. In terms of measurements performed back-to-back , the particles of the world 'switch' instantly from one eigenstate to the next. But the Schroedinger wave alone does not actualyl contain this instantaneous switching. The schroedinger wave moves around in any configuration.. not just standing waves

So we are stuck with this picture of matter and energy where the particle is in an eigenstate WHEN WE MEASURE IT, but it is "smeared out wave" when we are not measureing it. {{edit : use consistant formatting and no capitals}}

{{ rephrase all of this paragraph }} plato wrote that we don't experience reality directly, but only shadows ona cave wall. You might think we have since resolved that issue with our fancy modern science. But no. It remains unresolved even today. We don't know if the schroedinger wave is what the universe is "made of" or whether the particles are what the universe is "made of"

If the universe is made of particles, then the schroedinger wave is a MATHEMATICAL description of their behavior. A 'law' not a 'thing'.{{ edit consistant format }}{{ add there schro is merely only a computing device on teh chalkboard. A mere mathematical description. }}

So over the course of a few days, you run in mental circles with Quantum Mechanics, not knowing whether the world around is 'made of math' or 'made of stuff'. there is no easy or apparent resolution.

Studying modern physics does not resolve these questions. It makes them WORSE. If you grasp tightly onto the idea that "particles exist and teh schroedinger wave is a mathematical entity" then entanglement will not fit into that picture.

Entanglement

Etanglement strong suggests that the schroedinger wave is the real thing, and that particles are "shadows on teh cave wall" (so to speak) This is the 'way' particles are in that annoying gap between measurements. IF you have two seperates particles in a lab, and you do something to them where you cannot know which state they are in, you have 'entangled' them, and QM says what they do now is act as if they are a single physical system rather than two seperate ones.

This is indeed what we measure in labs. If Alice has an atom that is entangled with Bob's atom, then when alive measures her atom as "spin up" that measurement will effect the probability that Bob's atom is in spin up state also, even when they are far apart.

Re: the Cheshire Cat smiles

"When we measure the physical world , we always find it made up of particles. But when we are not measuring it, the particles become an amorphous wave. The particle's positions and states are only smeared out probabilities -- even their individual identities as particles dissolves."

Re: the Cheshire Cat smiles

You are able to save drafts, multiple drafts. The Save button is next to the "preview" and "Submit" of any post. Please do so in order to format, compose your posts rather than posting in the Lounge. Thank you for your cooperation.

Re: the Cheshire Cat smiles

You are able to save drafts, multiple drafts. The Save button is next to the "preview" and "Submit" of any post. Please do so in order to format, compose your posts rather than posting in the Lounge. Thank you for your cooperation.

mtb, does this mean that I can click Save and then close the window while I go to another web site to look up something? Then, I can come back to the draft that I saved? I'd like that. How would I get back to the saved window? Window? Should I say draft? How do I find it when I want to come back to it?

Saving Drafts

You are able to save drafts, multiple drafts. The Save button is next to the "preview" and "Submit" of any post. Please do so in order to format, compose your posts rather than posting in the Lounge. Thank you for your cooperation.

mtb, does this mean that I can click Save and then close the window while I go to another web site to look up something? Then, I can come back to the draft that I saved? I'd like that. How would I get back to the saved window? Window? Should I say draft? How do I find it when I want to come back to it?

Thanks.

Vivian,

Yes it means you can save it and go to another web site to look stuff up. You will find the drafts in your "User Control Panel" on the "Front Page" is a section titled "manage drafts" From there you can load your draft or edit it again and again and again. :)

Re: the Cheshire Cat smiles

[quote=mtbturtle]Yes it means you can save it and go to another web site to look stuff up. You will find the drafts in your "User Control Panel" on the "Front Page" is a section titled "manage drafts" From there you can load your draft or edit it again and again and again. :)[/quote]

Gracious! I've been doing a lot of Copy/Pastes to deal with that. And I suspect that explains a lot of the multi-quotes I see others doing. Thank you very much. I shall try this.